Relay prototype

Considering getting this simple relay implementation into ThaliProject while I finish up the other aspects of it - to simplify folks using the HTML5 seed.   Perhaps into a new branch on ThaliProject - but then you wouldn't be able to see the diff for review.

Only one source file here for the relay - RelayWebServer.java (and RelayWebServerTest.java).  The other bits are all NanoHTTPD.  Open questions on code file headers for those....
We'll have to investigate a bit, I vaguely remember that Pouch had forced this in several places and will refuse to talk to you if you don't give back an allow-credentials:True    - depending on how we do the adapter we could fix that, although it may be harder unless we replace their XHR code rather than just shimming in front of it.